Field of the Invention
The present invention relates to a display device to be used, for example, in an operation panel of a multifunctional digital image forming apparatus (i.e., a multi-function peripheral abbreviated as MFP) having multiple functions such as copier function, printer function, facsimile function, and scanner function, a screen display method for the display device, a recording medium, and an image processing apparatus.
Description of the Related Art
The following description sets forth the inventor's knowledge of related art and problems therein and should not be construed as an admission of knowledge in the prior art.
The MFPs have displays of different sizes (with different display resolutions) on their operation panels, have different functions, and make prints at different speeds depending on the model. Workplaces of a large business company are ordinarily equipped with image processing apparatuses of various models depending on the number of workers and the purpose of use.
With different user interfaces depending on the model in such an environment, users would be bothered so much by learning the use of them.
As a common method to solve such a problem with the image processing apparatuses having displays with different display resolutions, identical firmwares are used in the image processing apparatuses. These firmwares store base screen images whose sizes are adjusted to one reference resolution so that the base screen images can be enlarged or reduced to the display resolutions of the displays.
This method, however, needs some extra time for a base screen image to be enlarged or reduced to the display resolution of the display if the display resolution is not equal to the reference resolution; a screen thus appears on the display slowly. As is obvious, slow screen display impairs usability. A base screen image can be enlarged or reduced quickly to avoid slow screen display but only to sacrifice image quality and usability.
As a solution to these problems, Japanese Unexamined Patent Application Publication No. 2003-256827 teaches a technique that achieves quick screen display without sacrificing image quality. In this technique, when an application is launched for the first time, a low-quality screen image is created and displayed by quick enlargement or reduction, and a high-quality screen image is then created and stored on a cache memory. When the application is launched for the subsequent times, the high-quality screen image stored on the cache memory is displayed on the display means.
This technique, however, still leaves the following problem unsolved when it is applied to an image processing apparatus configured to switch between many settings screens on its display. That means it is a costly alternative because this image processing apparatus needs to have a cache memory that is large enough for many images.
As a solution to this problem, Japanese Unexamined Patent Application Publication No. 2015-011605 teaches a technique that achieves saving on memory space on a cache memory by erasing an image from the cache memory. Specifically, when the cache memory does not have free space enough for another image, such space is ensured by erasing an image that requires the user take many operation steps to reach the target screen or erasing an image that requires the user to take a certain number of operation steps or more to reach the target screen, from the cache memory. Another image can be thus stored on the cache memory.
According to Japanese Unexamined Patent Application Publication No. 2015-011605, an image to be erased from the cache memory is determined with reference to the number of operation steps to be taken. This technique, however, still leaves the following problem unsolved.
That is, the image processing apparatus needs to switch between many settings screens to advance a job. For example, users ordinarily check for an error in address settings and correct if any in order to prevent leaks of classified information, and also check for an error in printer settings and correct if any in order to avoid waste of paper. In the technique taught in Japanese Unexamined Patent Application Publication No. 2015-011605, images that require the user take more operation steps, even if they are more likely to be used later, are automatically erased. Such images will therefore need to be recreated at a high resolution.
Furthermore, there are screen images that do not deserve to be stored on the cache memory for later use. For example, a warning screen, which is independent of tree structure, can be displayed after any screen but is rarely displayed. It is therefore irrational to store an image of this screen on the cache memory. The image processing apparatus is configured to further display a preview screen that allows a print review of a scanned document and a thumbnail view screen that allows an at-a-glance view of scanned images stored. These screens hardly can reflect images with a high degree of accuracy because of the limited display screen, and such images do not need to have a high image quality. It is therefore irrational to store them on the cache memory as well.
In contrast, in the techniques taught in Japanese Unexamined Patent Application Publications No. 2003-256827 and 2015-011605, high-quality screen images are created and stored on the cache memory even if they are screen images not deserving to be stored on the cache memory, resulting in waste of cache space.